410 FV - Mercruiser Repower 375 HP or Rebuild 420 HP?
Treemagnet
Member Posts: 14 ✭✭
Yesterday wasn’t our greatest day on the water…our port engine threw a rod that left a baseball sized hole in the block. The engine (8.1L H/O 420 HP) was 11 years old with 685 hours and had always been in freshwater…way too new to croak.
Mercruiser remanufactures an 8.1L “Plus Series” motor using a reclaimed block with new everything (electrical, MPI, etc.), so nothing from the old engine must be used.
The Plus Series motors come with a 3 year warranty. However, the HP rating is only 375, which is 45 HP less than our deceased motor.
Will the HP difference work and play well with the starboard motor that has 420 HP?
If okay, will one or both need to be re-propped?
Will the lower HP just not be sufficient for the boat…or cause it to be run too near max?
I can get a 420 HP Plus Series, but it is an extra $3000 and only comes with a 1 year warranty.
Or, since it’s only been in freshwater, should I just go with a remanufactured long-block and move everything over from the old engine. I’m not leaning this way, given the age of all the existing components.
Anyone know how they can get the engine out/in through the opening…it definitely is not large enough?
Thanks in advance for your help!
David
Comments
Well, sorry to hear about the troubles. I would be a bit leery going with less horsepower because the 410/420 style boat is very heavy and a lot to push (heck, I have the same horsepower on mine and wouldn't go less).
Is there no way of getting the same block new and just replace that?
Dream 'Inn III -- 2008 400 Express
Yeah, this boat is extremely heavy, hence my reticence to go with the smaller engine. Thank you both...hopefully we'll hear from Alswagg soon.
Treemagnet - I would not replace the motor with one of lesser HP. I would think that both motors must be matched or you will always be working the lower HP motor harder (more throttle) at almost any given speed. Additionally, I agree with Dream that, due to the size and weight of the 410 you want all the HP you can get. I wouldn't be afraid of getting the short block and using the external components from the old engine. 685 hours isn't a lot of run time for things like alternators, starters, etc. In the automotive repair business external parts are frequently reused when short blocks are installed, even on vehicles with much more use than your boat has seen so far.
I'm sorry to hear that your motor failed. Was there any indication prior to it self destructing like knocking or other noises?
There were absolutely no indicators. The engine sounded and ran perfectly, the temp gauge was at 178, and there were no alarms before we heard the bang. Thanks
Today, the marine repair facility will inspect for signs of prop trauma and, if so, we'll pursue an accident claim. The prior week the area received 3.5 inches of rain, so it is possible there was some slightly submerged debris. The water depth was over 120', but we did see a carpet floating about 10 yards behind the boat after the incident. It is possible we hit the carpet, but couldn't see whether it appeared to have been shredded or torn by the prop and, unfortunately, it sunk before we could get to it. Thanks
Thanks Rasbury, wm61356, and SeaHare, for reassuring me that swapping components is reasonable, because that will save significant $. I'm fairly certain that is what the insurance company will do if this ends up an accident claim.
The boat is on Lake Travis (Austin TX) and we just had to take advantage of a rare windless 75 degree December day, as we only get 2 to 4 each year. Did my time in cold climates and empathize with everyone now dealing with winter's blustery ways. Then again we pay with REALLY warm summers, but I'm okay shoveling heat.
The verdict is in. We hit nothing. The port engine just decided it was time to reject a rod and empty our wallet. Going with a Mercury remanufactured Pro-Series Longblock (420 HP), since they come with a legitimate warranty. The only thing left is to determine the cause to prevent reoccurrence....oh yeah...and win the lottery to pay for this monster. Thanks to everyone for your input. Will keep you all up to date on progress.
The other thing is this. Say you do put a 370 replacement block in there. You live with the issues and accept its drawbacks. What happens when you go sell the boat and the "survey says" ....... the boat has one 370hp motor and one 420hp motor. I personally would walk away from the deal.
no one said boats are cheap, but if you plan on keeping it, or plan on selling it. You need to do the right thing and bite the bullet. Sorry, that's probably not what you wanted to hear.
We will stick to our original plan and keep this boat for the long term. That means it will get everything done to prevent any issues in the next 3-4 years...new impellers for the other engine and genset, fluids flushed & changed (transmissions, other engine, and genset), new bottom paint, pull, clean, and test both engines' fuel injectors...pretty much everything. Of course we'll do new impellers and oil each year, or every 50 hours.
Anything else you all recommend?
where did the block vent? what shape is the hole?
Attached are pictures of the culprit...both rods are clearly. What is most noticeable is the chunk of crankshaft (which was visible and sticking out through a 6" hole in the oil pan after the engine blew) that just sheared off. This is what the technicians believe was the weak link that caused the issue, as there were no other signs...no burnt pistons, no scored cylinders, and no lack of oil (changed less than 15 engine hours prior).
The new long block, complete with all parts, has been installed. The fuel injectors (for both engines) were cleaned and pressure tested at an outside lab prior to reinstallation. Of course, both V-Drives will be flushed and filters replaced. In addition, the Starboard engine and genset now have new oil, impeller, and filter. Finally, we did new bottom paint.
They plan to have her tested and ready to roll by early next week. So, now with a completely clean slate and a lot of prayers, we'll have a far more positive maiden voyage (do-over). I promise to let you all know how it goes. Last but not least, thanks to everyone for your time and comments in helping me through this process. It was good to know you all were there!
I believe you nailed it BellevilleMXZ. My phone took the picture above. So, I just shot a 24MP photo and magnified on a high def monitor it clearly displays what appears to be an obvious casting flaw (maybe from an air bubble). The two engines had sequential serial numbers and this cost $25K to fix...so I'm praying this "flaw" doesn't also exist in the starboard engine's crankshaft. Yep, praying real hard!